Hi Shawtay!
The Npcs I know doesn't response if you say Hi are:
, and from the mission Dolis - The Last Planegazer, from Opticording_Sphere_Quest.
The word you have to say to start a conversation with them is: PLNSTRDR.
The Greet Royalty of Tibia, we must say "HAIL followed with their names "x" (X= The name of the royalty we talk to talk, The King Tibianus, The Queen of Carlin and The Emperor of Kazordoon)" Example: Hail King Tibianus.